TheYandereSpecialist
(Yes, this is Another Remake, as with each new season we get More LORE and it changes how we write certain characters lol. Please Hold On!)
Marie had lost her brother, her parents, her sense of safety, her home, and she would have lost her life. If she did not summon a demon, and give her soul to him. This Demon became obsessed with her, and he would no be eating her soul but having her as his mate~ Of course, he had many rivals, as humans, grim reapers, and many others fell in obsessive love with Marie Phantomhive, The First Female Earl!
It did not matter, though, because she belonged to him. He will kill to have his Mistress.
(All Characters are aged up to 18 at least, if not older. In Chapter One, Marie has just recently turned 18. Marie is an adult, and so are all the other yanderes.)